Telephone system



y 19, 1942- M. E. IMOHR 2,283,610

mia'monz" SYSTEM Filed Feb. 2, 1940 2 Sheets-She e t 1 a I a T m" f I \j[5 :50 F K T INi/ENTOR B M E MOHR ATTORNE May 19, 1942. v

M. E. MOHR 2,283,610 TELEPHONE SYSTEM Filed Feb. 2, 1940 2Shee(.s-Sheer. 2

INVENTOR y ME. om?

ATTORNEY Patented May 19, 1942 2,283,610 TELEPHONE SYSTEM Milton E.Mohr, Jamaica, N. Y., assignor to Bell Telephone Laboratories, York, N.Y., a corporation of New York Incorporated, New

Application February 2, 1940, Serial No. 316,903

11 Claims.

This invention relates to telephone systems and particularly toimprovements in systems for identifying subscribers on party lines.

An object is to increase the reliability and effectiveness of theidentification tests used for determining the calling subscribers onparty lines.

Heretofore various systems have been provided in which tests wereperformed by employing devices at the different party line stations forproducing oscillations on the line, the frequency of which differsaccording to which station is calling. These oscillations becomeefiective when a party is'calling by the application of direct currentor alternating current at the central ofiice in various manners toidentify the calling line. Some systems of this kind employ variouslytuned reeds at the substation for producin the oscillations which may bedetected at the central olfice for identification of a calling party.The reeds may be operated by the operation of a dial at the substationor by the operation of separate levers. The reeds may be arranged tointerrupt the line or act in the magnetic field of a coil to produce theoscillations.

According to the present invention advantages are obtained over theseprior arrangements by utilizing a party line identification system inwhich a vibratory reed of a different natural frequency'is provided ateach subscribers station, with means for plucking the reed at thecalling station when the dial returns to normal after having beenoperated to send the digit. The vibratory reed sets up in a coilelectrical oscillations of a frequency corresponding to the naturalfrequency of the plucked reed.

It is a feature of the present invention to provide means at the centraloflice comprising a selector and a register associated therewith whichresponds to such oscillations for identifying the calling station on aparty line. The arrangement is such that this register is not activelyconnected to the line until after the selector has been operated by dialpulses, to prevent false oscillations,

a selector and register circuit, embodying the applicants invention. VReferring to the drawings, a party line. has been shown with onesubscriberfs station circuit in detail, and a line finder connectedthereto which has only been illustrated by means of the terminals forthe party line and brushes for the line finder. 4 A selector circuit hasbeen shown for connecting the party line through the line finder tocircuits beyond, which have been indicated merely in a diagrammatic formas leading to a called subscribers line. A registering deviceconnectable to the selector for identifying acalling line has been shownin detail in accordance'with the applicants invention.

Referring to Fig. 1, a dial I has been shown in which the usualfinger-wheel 2 is attached to the hub 3. To this hub 3 is connected atrigger v l operated upon by a spring 5 so that when the finger-wheel 2is moved in the clockwise direction to send a digit, this trigger 4 willpass by a reed 6 without causing it to vibrate but on the return of thedial to normal, the trigger will pluck the reed and cause it to vibrate.The reed is mounted in a coil 1 which is provided with magnetic returnpole-pieces 9 that may be connected in any suitable manner to the reedand to the side. of the dial structure. This (5011 is connected acrossthe line conductors as shown at the substation A in Fig. 2, so that themechanical vibrations of the reed will, by acting in the electromagneticfield between the pole-pieces, set up in the coil elecdue to the dialingover the line, from being picked up by the register. Service meters maybe provided in the line circuit to be controlled by the tricaloscillations of a frequency corresponding to the natural frequency ofthe reed Referring now to the Figs. '2' and 3, the line finder. will beoperated to connect its brushes IE to the terminals l6 of the callingline when any one of the parties on this line removes his receiver fromthe switchhook-and any suitable line-finder circuit well known in theart may be used for this purpose. When this connection is establishedthe calling party, for example, party A of thefour parties A, B, C andD, will dial the first digit by operating the dial IT. This first seriesof impulses will operate theselector iii to selectas is V I 1 usual incircuits of this kind a group of trunk circuits-leading to secondselectors and hunt to find an idle one of these selectors andthesucceeding digits will operate the second selector and a connectorsuch as 22 to establish a connec-' tion to a called subscribers line 23as is well known in the art.

A description will now be made of the effect of the first digit toestablish aconnection by the selector 18 to a second selector and toconnect the register shown in Fig. 3 to this selector I9 at the end ofthe digit to identify the calling party and record the call.- When theconnection is extended to the first selector I8 a circuit is completedfor the operation of relay 26 from battery through the lower winding ofthis relay, contacts of relay 21 over the ring conductor, over the linfinder through the calling subscriber's loop, back over the tipconductor, over the line finder, contacts of relay 21, upper winding ofrelay 26 to ground at the eleventh rotary step contacts 39 of theselector. Relay 25 closes a circuit for the operation of relay 32 frombattery through th winding of this relay, contacts of relay 26 and 21 toground. The register circuit shown in Fig. 3 is provided with vacuumtubes I99 and I9I and also a cold cathode tube I93, the purposes ofwhich will become apparent hereinafter. The grid of tube I99 is normallynegatively biased by being connected to battery through the winding ofrelay 32 so that the tube is normally not conductive, but itshould benoted-that on the operation of relay 26, a circuit is completed for thisgrid from ground through contacts of relays 21 and 26 causing current toflow through the winding of relay 32 and consequently this negative biasis reduced to zero making the tube conductive. This causes theoperationof relay I94 from battery through the winding of this relayover the plate and filament circuit to ground. The operation of thisrelay I94 relay 34 and vertical magnet 35 become operated I from batterythrough the windings of this magnet and relay in series through contactsof rebattery, winding of this relay, off-normal contacts 31, contacts ofthe rotary magnet 49, contacts of relays 39 and 21 to ground. The gridof tube I9I is now connected'to ground through the offnormal contacts 31and contacts of relays 34 and 32 to ground or through contacts of therotary magnet 49 and contacts of relays 39 and 21 to ground, thusremoving the negative bias normally on this grid as applied through the.winding of relay 39 from battery. Tube I9I now becomes conductive andcloses a circuit for the operation of relay I95 from battery, winding ofthis relay over the plate, and filament circuit to ground. Relay 26 nowoperates at the end of the first impulse and releases and operates inresponse to the succeeding impulses of the first digit and alternatelyoperates. and releases the vertical magnet 35 to advance the brushes ofthe selector I8 to the desired group of second selectors. Relay I94 thusoperates and releases for each impulse transmitted while relay I95remains operated during the transmission of the impulse of the firstdigit as relay 34 is slow in releasing and remains operated during thistransmission of the succeeding impulses and as long thereafter as relay34 remains operated. In addition, relay I95 remains operated due to itsslow-to-release characteristics during the succeeding hunting operationseven though relay 39 releases and operates alternately during theseoperations as hereinafter described. When relay 26 operates after thelast impulse is received, tube I99 becomes conductive and relay I94 nowremains operated during the succeeding hunting operations of theselector and the vertical magnet 35 and relay 34 release. Relay 34 inreleasing closes a circuit for the rotary magnet 49 from battery,winding of this magnet, contacts of relays 39, 34 and 32 to ground. Therotary magnet now operates and opens the locking circuit for the relay39. Re-

lay 39 therefore releases causing the release oi the rotary magnet 49.The operation of rotary magnet'49 advances the brushes of the selectorto the terminals of the first circuit to a second selector. If thisselector is busy there will be a ground on the sleeve terminal 4|thereof so that when the rotary magnet 40 releases a circuit for relay39 is again closed from battery through the winding of this relay,Vertical off-normal contact 31, contacts of the rotary magnet 49,contacts of relay 21 to the sleeve brush of the first selector and thesleeve terminal 4| to ground. Relay 39 in operating closes the lockingcircuit through its upper armature and front contact and operates therotary magnet 49 over the circuit before traced so that selector I8 willnow take a second step. However, if the circuit leading to this secondselector is idle, there will be no ground on the sleeve terminal 4| andconsequently when the relay 39 releases on the operation of the rotarymagnet 43, it will not be reoperated and thus prevents the selector fromtaking another step. It should be noted now that on therelease of relay39 relay 21 will operate over a circuit from battery through the windingof relay 39, vertical off-normal contacts 31, contacts of the rotarymagnet'49, winding of relay 21, eleventh step rotary off-normal contact43, contacts of relay 32 .to ground. The electrical characteristics ofrelay 39 are suchthat this relay will not operate at this time. Relay 21in operating opens the circuit for relay 25 which now releases, causingthe release of relay 32. Relay 21 is maintained operated over the groundfrom the sleeve at'the second selector, contacts of relay 21 through theeleventh rotary step contacts 43, winding of relay 21, contacts ofrotary magnet 49, vertical off-normal contacts 31, winding of relay 39to battery. This ground on the sleeve terminal 4| makes the seizedsecond selector busy. On the operation of relay 21 the ground connectionfor the grid of tube I99 is removed and consequently tube I99 becomesnon-conductive and relay I94 releases. By examining the circuits asdescribed it will be noted therefore that while the tube I99 andrelayI94 follow the pulsing, the tube I99 will remain conductive and relayI94 remains operated during the above-described hunting operation andreleased at the end of these operations, that is when relay 21 operates.The relay I05 which is slow in releasing will remainoperated during thepulsing operations, as well as during the hunting operations, eventhough the tube I91 will alternately become conductive andnon-conductive due to the opening of the pulsing circuit by the rotarymagnet 49. The relay I will, of course, release on the final release ofrelay 39. I

The registration for identifying the calling subscriber will take placeimmediately afterdialing of the first digit ceases andthe operationsto'this effect are as follows: When relays I94 and I95 are firstoperated a circuit is completed from battery through contacts of relay Ithrough the condenser I06, resistances I01 to ground through the contactof relays 26 and 21, thus causing the charging of the condenser I06.-However, this condenser is slow in charging so that it'will not be fullycharged to break down the control gap between the electrodes I08 and I09of the tube I03 before relay I04 releases due to the tube I00 becomingnon-conductive as the ground is removed at contacts of relay 26. Whenrelay I04 releases, the condenser I06 discharges through contacts ofthis relay. These operations take place repeatedly during the dialing ofthe digit. -However, as soon as the dialing is completed as described,relay I04 remains operated for a longer period, permitting the condenserI06 'to fully charge and ionize the control gap between the electrodesI08 and I09 of tube I03 and thus closes a circuit through the main gapfor the main electrode IIO for the operation of relay I I2 from battery,contacts of relays I05, electrodes I09 and H0, winding of relay II2 toground. Resistance place the moment relay 26 is released on the op- I I3is inserted from battery through the contacts 7 of relay I05 of thecircuit for relay II2 to partly energize this relay and secure a quickoperation thereof when the tube I03 ionizes. Thus relay I I2 will not beoperated until the completed.

The electrical oscillations received from the calling subsc'ribersstation as produced by the vibration of the reed 6 in the coil I are nowtransmitted as soon as the dial returns to normal over the tip and ringconductors. These oscillations are, of course, different for eachcalling station as the reeds are differently tuned and are transmittedthrough the contacts of relay 21, condensers H5 and H6, contacts ofrelay II1, which was operated by an obvious circuit through contacts ofrelays I 04 and I05, and repeated through the repeating coil I I8through the bandpass filters II9, I20, I2I or I22, and repeated throughthe step-up transformers I23, I24, I or I26 to the amplifier-detectorsI21, I28, I29 or I30 over circuits closed by relay I32 which it will benoted is energized over an obvious circuit closed by relay I I1.Depending, however, on the characteristics or frequency of theoscillations received one of these filter and amplifier-detectorcircuits will respond and cause the associated relays I33, I34, I35 orI36 to operate to start the identification of the calling party. If thefirst party A is the one calling, it may therefore be assumed that theamplifier-detector I21 will be operated to close a circuit forthe'operation of relay I33 at this time. Relay I33 now closes a circuitfor an associated relay I31 from battery through the right-hand windingof this relay, contacts of relays I33, I38, I39, I40 and MI to ground.Relay I31 in operating closes a locking circuit for itself from batterythrough its righthand winding and. left-hand armature and front contact,through contacts of the relays I38, I33, I40 and IM to ground atcontacts of relay I04. The operation of relay I31 now closes a circuitfor the operation of the associated relay I M from battery through thewinding of this relay,

contacts of relays II2, I31 to ground at relay I42 and relay I4I closesa locking circuit from battery through itswinding and inner left-handarmature and front contact to ground at relay 46. When relay I4Ioperates, the locking circuit for relay I31 is opened and this relay I31may now release as the relay I33 releases as soon as the oscillationsfrom the calling subscriber ceases. The relays I04 and I05 are now notneeded so dialing has been,

eration of relay 21 and tubes I00 and IOI'become non-conductive.Similarly, tube I03 becomes non-conductive on the release of relay I04,and relays H2, H1 and I32 release. The operation of the relay I4Ithereforedisconnects or disables the register in regard to any effectsthereon that may be caused from transients in the tip and ring conductorduring the hunting operations as such transients, while they maypossibly operate relays I 33, I34, I35 or I36, relays I31, I43, I44 orI45 will not operate as their operating circuits are open at contacts ofrelay I4I.- If it should happen that any two of the relays I31, I43, I44or I45 would operate during the identification period due to anytransients that may occur, the relay I42 would operate over a circuitfrom battery, winding of relay I42, contacts of these relays throughresistances to ground. This would prevent any of the relays I4I, I40,I39 or I38 from operating. It should also be noted that during thepulsing period of the first digit, no registration can take place due toany transient that may be received during dialing. Should such falsefrequencies arrive, the detecting circuits may pick up the frequenciesand cause the corresponding relays I31, I43, I44 or I45 to operate butas relay II 2 is not operated at this time, no registration can takeplace.

The calling line is now connected through the selector I8 over contactsof relay 21 to the second selector and the succeeding series of digitsmay be dialed as is well known in the art to operate the second selectorand a connector such as 22 to establish a connection to the calledsubscribers line 23. It should be observed that when the ground wasapplied to the sleeve circuit for the second selector, relay 49 operatedfrom battery, winding of this relay, contacts of relay 46 to ground.This relay closes a substitute ground for maintaining relay I4Ioperated. Now, therefore, when the called subscriber at 23 answers, areversal of the current over the connection causes the relay 50 tooperate. This in turn closes a circuit for relay 46 which in operatingopens the ground connection through its con-- that relay 5| will havetime to close a connection from battery, contacts of this relay,contacts of relay I4I over a terminal of the line finder'and the windingof the corresponding meter 52 to.

ground to cause this meter to operate and register the call before relay49 releases to release relay I4I. When relay 49 releases, the relays MIand 5| release and relay 49'provides a looking circuit from battery,inner right-hand armature and front contact of this relay, right-handarmature and back contact of relay 49, outer right-hand armature andfront contact of relay 46 to ground on the sleeve.

When the subscriber releases the connection by hanging up the receiver,the ground on-the sleeve is removed and relay 21 releases. This in turncloses the circuit for the release magnet 53 from battery through thevertical off-normal contact 54, contacts of relays 32, 26 and 21 toground. The release magnet returns the first .selector I8 to normal andthen releases due to theopening of the vertical off-normal contacts 54.Similarly, due to the removal of the ground from the sleeve connection,relay 46 releases and all the circuits are now restored to normal, the

second selector, connector 22 and the line finder being returned tonormal in the usual manner.

Although the mechanism for identifying the calling party is shown hereinas being connected directly to the link between the line finder andselector 20, it will be understood that this mechanism may be common toa plurality of these links and may be associated with a link when neededby the usual selecting switches or relays.

What is claimed is: t

1. In a telephone system, a line having a plurality of subscribersstations, a vibratory reed at each station having a different naturalfrequency, a dial at each station adapted to vibrate the associated reedafter the dial has been operated to send a digit, means responsive tothe vibrations of the reed for causing in the line oscillations of afrequency corresponding to the natural frequency of said vibrating reed,a station identifying register, means responsive to said oscillationsfor operating said register to identify the calling station, means forpreventing said oscillation responsive means from operating to registerfalse oscillations in said line caused by the digit transmission, andservice meters controlled by said register.

2. In a telephone system, a line having a plurality of subscribersstations, a vibratory reed at each station having a different naturalfrequency, a dial at each station adapted to vibrate the associatedreed, means responsive to the vibrations of the reed for causing in theline oscillations of a frequency corresponding to the natural frequencyof said vibrating reed, a station identifying register, means responsiveto said oscillations for operating said register to identify the callingstation, and means controlled by said dial pulses for preventing theoperation of said register by any false oscillations that may occur onthe line during the dialing period.

3. In a telephone system, a line having a plurality ofsubscribersstations, a vibratory feed at each station having a differentnatural frequency, a dial at each station adapted to vibrate theassociated reed after the dial has been operated to send a digit, meansresponsive to the vibrations of the reed for'causing in the lineoscillations of a frequency corresponding to. the natural frequency ofsaid vibrating reed, a station identifying register, means controlledduring the dialing period for preventing transient oscillations fromreaching the register and controlled after the dialing period forpermitting the register to be operated by the oscillations caused by thevibration to identify calling stations, and service meters controlled bysaid register.

4. In atelephone system, a line having a plurality of subscribersstations, a vibratory reed at each station having a different naturalfrequency, a dial at each station adapted to vibrate the associatedreed, means responsive to the vibrations of the reed for causing in theline oscillations of a frequency corresponding to the natural frequencyof said vibrating reed, a station identifying register, circuit meansincluding two Vacuum tubes operative in one manner during a dialingperiod for preventing transient oscillations from reaching the registerand operative in another manner after the dialing period to permit theregister to respond to the oscillations caused by the vibrating reed toidentify the calling station, and service meters controlled by saidregister.

5. In a telephone system, a line having a plu- .rality of subscribersstations, a vibratory reed ateach station having a different naturalfrequency, a dial at each station adapted to vibrate the associated reedafter the dial has been operated to set a digit, means responsive to thevibrations of the reed for causing in the line oscillations of afrequency corresponding to the natural frequency of said vibrating reed,a station identifying register responsive to said oscillations toidentify calling lines, a normally open circuit for connecting saidregister to said line, means for closing said circuit after the dialingperiod to permit said oscillations to be transmitted to said registersto operate it to identify the calling line, and service meterscontrolled by said register.

6. In a telephone system, a line having a plurality of subscribersstations, a vibratory reed at each station having a different naturalfrequency, a dial at each station adapted to vibrate the associatedreed, means responsive to the vibrations of the reed for causing in theline oscillations of a frequency corresponding to the natural frequencyof said vibrating reed, a selector circuit responsive to the dialing ofa digit for establishing connections beyond, a station identifyingregister associated with said selector and responsive to saidoscillations to identify calling lines, means controlled by saidselector after a digit has been dialed for connecting the register tothe line so that the register will respond to said oscillations toidentify the calling line, and service meters controlled by saidregister.

'7 In a telephone system, a line having a plurality of subscribersstations, a vibratory reed at each station having a difierent naturalfrequency, a dial at each station adapted to vibrate the associated reedafter the dial has been operated to send a digit, means responsive tothe vibrations of the reed for causing in the line oscillations of afrequency corresponding to the natural frequency of said vibrating reed,a selector circuit responsive to the dialing of a digit for establishingconnections beyond, a station identifying register associated with saidselector and connectable to said line and responsive to saidoscillations to identify a calling line, means operated during thedialing of a digit for preventing the connection of the register to theline and operative after the dialing period for connecting the registerto the line so that it will respond to said oscillations to identify thecalling line, and service meters controlled by said register.

8. In a telephone system, a central office, a plurality of lines some ofwhich are party lines, a vibrating reed at each of the stations on aparty line, a dial at each party line station, means controlled by thedial at any one of the stations of a party line for transmittingimpulses over said line representing different digits and for startingthe associated reed to vibrate at its natural frequency after theimpulses have been transmitted, means responsive to the vibrations ofany one of said reeds for causing in the associated line electricaloscillations of a frequency corresponding to the natural frequency ofsaid vibrating reed, means at the central office responsive to saidimpulses for selecting a corresponding group of lines and for thereafterestablishing a connection from the calling party line to an idle one ofsaid selected group of lines, means for establishing a connection fromsaid selected line to a called line, a station identifying register atsaid central office and means responsive to said oscillations foroperating said register to identify a calling station, means forenabling said last-mentioned means when the group of lines has beenselected, a service meter for each of the subscribers stations of saidparty lines, and means responsive to the setting of said registers foroperating the corresponding service meter when the connection has beenestablished through to a called subscriber and the called" subscriberhas answered a call.

9. In a telephone system, a line having a plurality of subscribersstations, a dial at each station for producing dial pulses, said .dialhaving a coil connected to the line, a vibratory reed I in said coil andmeans for plucking the reed operative inresponse to the movement of thedial on its return to normal after the dial impulses have been produced,said plucked reed serving to cause electrical oscillations correspondingto its natural frequency in said line, the natural frequency of the reedin each dial being different from that of any of the others,

a station identifying register, means responsive to said oscillationsfor operating said register to identify the calling station, and meansfor preventing said oscillation responsive means from operating toregister false oscillations in said line caused by the digittransmission.

' 10. In a telephone system, a line having a plurality of subscribersstations, a dial at each station for producing impulses, said dialhaving a coil connected to the line, a vibratory reed in said coil andalever mechanism associated with said dial for plucking said reed afterimpulses have been produced on the return movement of the dial to normalto cause in said line electrical oscillations corresponding to thenatural frequency of the plucked reed, the natural frequenoy of the reedin each dial being different from that of any of the others, a stationidentifying register, means responsive to said oscillations foroperating said register to identify the calling station, and means forpreventing said oscillation responsive means from operating to stationsfor connecting the associated party line to a called line, a vibratingreed at each party line station having a different natural frequency,means associated with each dial for vibrating the associated reed whiledialing, means responsive to the vibration of a reed for causing on theassociated party line, oscillations of a frequency corresponding to thenatural frequency of said reed, a party line station identifyingregister associated with said switching means, means responsive tooscillations on a party line originating only from a vibrating reed foroperating said register to identify the calling party line station andoperative only after the dialing of a first digit is completed, servicemeters controlled by said register and means for operating a servicemeter in accordance with the setting of the record on said register, tometer the identified

